我是Hibernate注释的新手，我想尝试一个例子。
我有两个类(Node和HyperEdge)，当我运行应用程序时，它只为Node创建一个表，而不是为HyperEdge创建一个表。
这是我开发的代码:
节点:import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="Node")
public class Node {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
@Column
private String name;
@Column(name=""group"")
private Integer group;
public Node() {
super();
// TODO Auto-generated constructor stub
}
public Node(Integer id, String name, Integer group) {
super();
this.id = id;
this.name = name;
this.group = group;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getGroup() {
return group;
}
public void setGroup(Integer group) {
this.group = group;
}
}
HyperEdge:
import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Table(name="HyperEdge")
public class HyperEdge {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
@Column
private String title;
public HyperEdge() {
super();
// TODO Auto-generated constructor stub
}
public HyperEdge(Integer id, String title) {
super();
this.id = id;
this.title = title;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
hibernate.cfg.xml:
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/exhiber</property>
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<property name="connection.pool_size">1</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="current_session_context_class">thread</property>
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">create</property>
<mapping class="com.hib.ex.entity.Node" />
<mapping class="com.hib.ex.entity.HyperEdge" />
</session-factory>
</hibernate-configuration>
HibernateDao:
import java.util.List;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import com.hib.ex.entity.HyperEdge;
import com.hib.ex.entity.Node;
public class HibExDao {
public void saveNode(Node noeud) {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
session.beginTransaction();
session.save(noeud);
session.getTransaction().commit();
session.close();
}
public List listNode() {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
List nodes = session.createQuery("FROM Node").list();
session.close();
return nodes;
}
public Node readNode(Integer id) {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
Node noeud = (Node) session.get(Node.class, id);
session.close();
return noeud;
}
public void saveHyperEdge(HyperEdge he, String chaine) {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
session.beginTransaction();
he.setTitle(chaine);
session.save(he);
session.getTransaction().commit();
session.close();
}
public List listHyperEdge() {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
List hyperedges = session.createQuery("FROM HyperEdge").list();
session.close();
return hyperedges;
}
public HyperEdge readHyperEdge(Integer id) {
SessionFactory sf = HibExUtil.getSessionFactory();
Session session = sf.openSession();
HyperEdge hyperEdge = (HyperEdge) session.get(HyperEdge.class, id);
session.close();
return hyperEdge;
}
}
主类:
import java.util.List;
import com.hib.ex.dao.HibExDao;
import com.hib.ex.entity.HyperEdge;
import com.hib.ex.entity.Node;
public class Run {
public static void main(String[] args) {
HibExDao dao = new HibExDao();
System.out.println("****************WRITING****************");
Node n1 = new Node();
n1.setName("toto");
dao.saveNode(n1);
System.out.println("Node saved!");
Node n2 = new Node();
n2.setName("lala");
dao.saveNode(n2);
System.out.println("Node saved!");
System.out.println("n****************READING****************");
List nodes = dao.listNode();
System.out.println("Name in Node number 2 is: " + dao.readNode(2).getName());
}
}
有什么问题吗?我该怎么补救呢?
谢谢!
也许你必须在HyperEdge类中添加@Entity注释
HyperEdge类中缺失的@Entity注释
@Entity注释用于将该类标记为实体bean。所以类至少应该有一个包作用域的无参数构造函数。
@Table注释用于指定保存数据的表。name属性指的是表名。如果没有指定@Table注释，Hibernate将默认使用类名作为表名。
在HyperEdge类中，您必须添加@Entity注释，以便hibernate可以将其作为实体与数据库中的表HyperEdge进行映射。
@Entity
@Table(name="HyperEdge")
public class HyperEdge {